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5. SCHC Compound ACK YANG Data Model

5. SCHC Compound ACK YANG Data Model​

This document also extends the SCHC YANG data model defined in [RFC9363] by including a new leaf in the Ack-on-Error fragmentation mode to describe both the option to use the SCHC Compound ACK, as well as its bitmap format.

5.1. SCHC YANG Data Model Extension​

<CODE BEGINS> file "[email protected]"
module ietf-schc-compound-ack {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-schc-compound-ack";
  prefix schc-compound-ack;

  import ietf-schc {
    prefix schc;
  }

  organization
    "IETF IPv6 over Low Power Wide-Area Networks (lpwan)
     Working Group";
  contact
    "WG Web:   `https://datatracker.ietf.org/wg/lpwan/about/`
     WG List:  <mailto:[email protected]>
     Editor:   Laurent Toutain
       <mailto:[email protected]>
     Editor:   Juan Carlos Zuniga
       <mailto:[email protected]>
     Editor:   Sergio Aguilar
       <mailto:[email protected]>";
  description
    "Copyright (c) 2023 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.
     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Revised BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (https://trustee.ietf.org/license-info).
     This version of this YANG module is part of RFC 9363
     (https://www.rfc-editor.org/info/rfc9363); see the RFC itself
     for full legal notices.
     ***************************************************************
     Generic data model for the Static Context Header Compression
     Rule for SCHC, based on RFCs 8724 and 8824.  Including
     compression, no-compression, and fragmentation Rules.";

  revision 2023-07-26 {
    description
      "Initial version for RFC 9441.";
    reference
      "RFC 9441 Static Context Header Compression (SCHC) Compound
                Acknowledgement (ACK)";
  }

  identity bitmap-format-base-type {
    description
      "Define how the bitmap is formed in ACK messages.";
  }

  identity bitmap-RFC8724 {
    base bitmap-format-base-type;
    description
      "Bitmap by default as defined in RFC 8724.";
    reference
      "RFC 8724 SCHC: Generic Framework for Static Context Header
                Compression and Fragmentation";
  }

  identity bitmap-compound-ack {
    base bitmap-format-base-type;
    description
      "Compound ACK allows several bitmaps in an ACK message.";
  }

  typedef bitmap-format-type {
    type identityref {
      base bitmap-format-base-type;
    }
    description
      "Type of bitmap used in Rules.";
  }

  augment "/schc:schc/schc:rule/schc:nature/"
        + "schc:fragmentation/schc:mode/schc:ack-on-error" {
    leaf bitmap-format {
      when "derived-from-or-self(../schc:fragmentation-mode,
                        'schc:fragmentation-mode-ack-on-error')";
      type schc-compound-ack:bitmap-format-type;
      default "schc-compound-ack:bitmap-RFC8724";
      description
        "How the bitmaps are included in the SCHC ACK message.";
    }
    leaf last-bitmap-compression {
      when "derived-from-or-self(../schc:fragmentation-mode,
                        'schc:fragmentation-mode-ack-on-error')";
      type boolean;
      default "true";
      description
        "When true, the ultimate bitmap in the SCHC ACK message
         can be compressed.  Default behavior from RFC 8724.";
      reference
        "RFC 8724 SCHC: Generic Framework for Static Context Header
                  Compression and Fragmentation";
    }
    description
      "Augment the SCHC Rules to manage Compound ACK.";
  }
}
<CODE ENDS>

Figure 9: SCHC YANG Data Model - Compound ACK Extension

5.2. SCHC YANG Tree Extension​

module: ietf-schc-compound-ack
  augment /schc:schc/schc:rule/schc:nature/schc:fragmentation/
        schc:mode/schc:ack-on-error:
    +--rw bitmap-format?        schc-compound-ack:bitmap-format-type
    +--rw last-bitmap-compression?   boolean

Figure 10: Tree Diagram - Compound ACK Extension

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